Wood-preserving apparatus



21 W BY Nov. 16, 1943. G. B. SHIPLEY 2,334,586

WOOD PRESERVING APPARATUS Filed Oct. 20, 1942 INVENT OR.

GPA/v7 5. JHIPLEY. WITNESSES.

M ATTOI-ENE KS.

Patented Nov. 16, 1943 UNITED STATES PATENT OFFICE woon-rnnsanvmo.APPARATUS Grant B. Ship-Icy, Pittsburgh, Pa.

Application October 20, 1942, Serial No. 462,742

1 Claim.

This invention relates to the impregnation of wood with preservatives tomake it'resistant to decay, insects, etc., and more particularly to amethod and apparatus for carrying out the treatment more safely thanheretofore. I

In order to increase the life of forest products by preventing decay anddestruction by insects, it is common practice to impregnate the woodwith a preservative such as creosote distillate, creosote, coal-tarsolution, and creosote-petroleum mixtures. Several different methods areused for forcing the preservativeiinto the wood, the most favored beingthe Rueping empty-cell treatment. In this method where air-seasonedtimber is being treated, the air pressure in the treating cylinder, israised to suitthe condition and species of Wood being treated. Forinstance, in treating pine the air pressure may be raised to 100 pounds,but with oak and hardwood 60 pounds issufficient. The treatingcylinder'isthen filled with preservative, and without lowering the airpressure, the preservative is forced into the wood by either a pressurepumpwhich forces addi-' tional preservative into the cylinder, or .byair' pressureon top of the preservative in the scale tank or pressuremeasuring tank connected" to the treating cylinder. When thepreservative pressure period is finished, the. preservative is removedfrom the treating cylinder and a vacuum is applied to remove the freepreservative remaining on the exterior of the Wood to prevent dripping.The preservative is heated in the cylinder and tankconnected to it.

The initial compressed air on the timber in the cylinder helps to openup the cells in .the'

wood and also acts as a vehicle for carrying the preservative into thecells. tive pressure period is finished, the air in these 'cells expandsand forces the surplus preservative out of them, leaving the Woodfibersimpregnated with preservative. This is often called jkickback. Forinstance, in the treatment of pine,

12 pounds of preservative may be forced into each cubic'fo'ot of thewood, but the kick-back" Wi'tlithis pro timber is usually conditioned inthe treating cylinderunder a steam pressure of 20 pounds gauge, Whereasfir and oak are completely immersed in a hot preservative oil and thenthe temperature. is gradually increased above the When the preserva-.

boiling point of water While the treating cylinder is under vacuum. 7

The treating cylinders and other closed pressure vessels used inconnection with Wood .preserving processes are usually equipped withsteamheating coils for the purpose of heating thepreservative to thedesired temperature. .Often, free carbon, wood chips, bark and dirtaccumulate in the bottom of these treating vessels around the steamcoils, with the result that when these coilsare not coveredwithpreservativethe carbon may become incandescentandglo-W and set fire tothe chips and bark, or sparks'from the tram car wheels and otherequipment entering the treating cylinder may cause a fire. There is alsoa possibility of static electricitycausing fires and explosions. In theheating of preservative oils, the gases which are formedin the treatingcylinder or in any other closed vessel Where air is being used present ahazard, depending upon the flash point of the various preservativesolutions and the temperatures involveddue to the necessary heating ofthe preservatives. Furthermore, the air from the compressor maysometimes be con taminated with poor lubricating oil, and it is knownthat in such cases serious explosions have occurred in the compressor,pipes, and air receiver. Fires at wood-preserving plants areparticularly disastrous and hard to control because of the great stocksof timber and highly inflammable preservative solutions.

It is among the objects of this invention to provide a method andapparatus fortreating wood in which the danger of fires and explosionsin the treating cylinder and. other containers is greatly diminished,and in which this result is accomplished in a simple and inexpensivemanner.

To accomplish the foregoing objects inert gases are substituted for air'for purging the treating cylinder and other vessels during the'cycle ofoperation and for putting pressure on the timber and preservative.Although a manufactured inert gas may be used,-it ispreferred to employWaste gas from the ,stack of the boiler that is a part of thepreserving. plant. To secure the proper inert gas from.boiler stacks,complete combustion of fuel should take place in theboilers. In order toavoid the possibility of sparks and hot cinders entering the system, theinert gas preferably is withdrawn frcmthe stack by a steam ejector Whichthen forces the gas into the treating cylinder or other vessels asdesired. The steam will destroy any live sparks and hot einders andatthe same time it will help purge the containers and eliminate thepossibility oi -any free carbon incandescence. The live steam helps topurify the gas, and the water used as a spray in the gas scrubber andcooler through which the gas is forced removes objectionable elementsand cools the inert gas before it goes to the compressor r treatingcylinder or other vessels. This same ejector can be arranged so that itwill also create a vacuum in the treating cylinder, etc., as needed. Thecompressor is used to deliver the inert gas to a receiver at suchincreased pressures as may be required in carrying on the various cyclesof operation used in the treatment of timber.

The preferred embodiment of the invention is illustrated in theaccompanying drawing in which the single figure is a diagrammatic viewof a wood bottom of the cylinder. By first connecting the ejectordirectly to the treating cylinder the capacity of the compressor need beonly about half of what it would have to be in case there were noejector.

If a higher gas pressure in the treating cylinder is now desired, valve36 is closed and valve 44 in pipe 28, valve 45 in pipe 2|, valve 4'6 inpipe 23, valve 4'! in pipe 25, and valve 48 in pipe 21 are opened. Thisconnects the ejector with the compressor and the latter with thetreating cylinder.

7 On the other hand, the compressor may be conpreserving plant with oneend of the treating cylinder open to show the wood being treated.

Referring to the drawing, the wood I to be treated is piled on a tramcar 2 and rolled on tracks 3 into a treating cylinder 4 which is thenclosed. The next step, when the empty-cell method is practiced asillustrated here, is to create a gas pressure in the cylinder to open upthe interstices of the wood. In accordance with this invention thispressure is created by forcing into the treating cylinder an inert gas.Preferably this gas is flue gas obtained from the stack Got the boilerplant I that forms a part of every wood preserving plant. To produce aproper inert gas, complete combustion of the boiler plant fuel shouldtake place. Therefore, the boiler should be equipped with the necessaryinstrumen-ts and apparatus for the efficient use of fuel, and this willalso result in more economical operation of the boiler.

In order to remove the gas from the boiler stack and force it into thecylinder, an ejector 8 is used which preferably is operated by dry steamsupplied from pipe 9 at a pressure of about 125 to 150 pounds. The gasinlet of the ejector is connected to the boiler stack by a pipe H, andthe outlet of the ejector is connected by a pipe l2 to the top ofcylinder 4. However, before the gas reaches the cylinder it preferablyis diverted through a scrubber l3 and cooler I l that are con-' nectedby pipes 16 and I7, respectively, to pipe l2 at points separated by anormally closed valve is. Some, and at times all, of the scrubbed andcooled gas may be diverted from pipe I! through a pipe to a pipe 2iconnecting stack pipe H with the inlet of a compressor 22. The outlet ofthe compressor is connected by a pipe 23 to a high pressure receivingtank 24 which in turn is connected by pipes 25, 26, and 2'! to pipe [2from the ejector.

Assuming, for the purpose of shortening this description, that allvalves are closed at the beginning of each step of the process and areclosed again immediately after the completion of each step, inert gas isdrawn from the boiler stack by the ejector and may be delivered directlyto the nected directly to the boiler stack by opening valves 49 and 50in pipe 2|, or it can be connected to an auxiliary source of inert gas,an inert gas. producer 5|, by opening only valve 55.

After the gas pressure within the treating cylinder has been raised thedesired amount, the

cylinder is filled by gravity with a suitable liquid preservative fromtank 55 by opening valves 56 and 57 in pipes 58 and 59, respectively,that connect the bottom of the tank with the bottom of the cylinder.Pipe 58 also leads to the bottom of a pressure measuring tank 60 filledwith preservative. Valves 3! and 48, and a valve 62 in a pipe 63connecting pipe 26 with the top of tank 55, are opened to allow thecompressed gas in the cylinder to move up into the tank as the cylinderis filled with preservative. Thus the preservative and compressed inertgas change places and the gas pressure is maintained.

To force the preservative into the wood, pressure measuring tank Si) isconnected to the bottom of the cylinder by opening valve 65 in pipe 58,and valve 57 in pipe 59. The preservative in this tank is forced intothe cylinder by high pressure inert gas from the receiver 24 to which itis connected by pipe 65, containing valve Bl, and pipes 25 and 26. Afterthe preservative in the cylinder has been under pressure the necessarylength of time, tank 55 is vented to blow off all gas to atmosphere byopening valve 62 and a valve 68 in a pipe 69 connecting pipe 26 with avent pipe 10 connected to pipe 16. Valves 56 and 51 are then opened sothat the pressure in the treating cylinder will force nearly all of theunused preservative therein up into tank 55. The high pressure gas onthe preservative in the pressure measuring tank 60 is then fed into thetop of the treating cylinder by opening valves 61, 48,

and 31 which will generally force the balance of the preservative upinto tank 55. However, if additional pressure is required, it can betaken from the receiver by opening valve 41. After the treating cylinderhas been emptied of all preservative it is vented to atmosphere byopening valves treating cylinder by opening valves 35, 35, 32, 33,

and 34 in'pipe II and valves 35, i9, and 31 in pipe l2. Or, valve l8 mayremain closed and valves 38, 39, and 40 in pipe l6,'and valve ll in pipell, opened so that the gas will be scrubbed and cooled before reachingthe cylinder. A large volume of inert gas is thus introduced into thecylinder, and the steam mixed with it helps wash and scrub the gas andto eliminate any sparks and hot cinders. Also, the steam helps purge thecylinder of explosive gases and destroys the in-, candescency of anyfree carbon that may occur as a result of the steam heating coil 42 inthe 48, and 68. To avoid waste and drippage of preservative after thepressure period is finished, and to help dry the treated timber, a quickfinal vacuum in,

the treating cylinder is created by drawing a vacuum or about 15 incheson the cylinder by means of the ejector to release the hot heavy vapors.

This is done by opening valves 12 and '13 m a ing this operation througha pipe 93 leading to I When the foregoing operating cycle has beenfinished, it is necessary to determine the net quantity of preservativeretained by the wood, and since before treatment the tank 55 wascompletely full and a known quantity of preservative was contained inthe pressure measuring tank, the treating cylinder is drained into thepressure measuring tank by opening valves 51 and 65. With gas pressurefrom receiver 24 on top of the preservative in the measuring tank thepreservative is forced up into tank 55 by opening valves 65 and 56. Withthe treating cylinder now emptied and tank 55 filled as at the start,the measuring tank is ready for the final measurement. The quantity ofpreservative remaining in the tank, when deducted from the initialamount, gives the net quantity of preservative retained by the wood. Themeasuring tank may then be filled with preservative from the working.

and storage tank 85 which is connected to the measuring tank through ageneral service pump 86 and a pipe 81 and pipe 58.

To facilitate deep and thorough penetration of the preservative in thewood by pressure processes, the timber should be seasoned and nearlydry, preferably air seasoned. Air seasoning is not always practicable,so, as a substitute, steaming of pine and boiling of fir and oak in thepreservative under vacuum will help remove the resin, juices, sap, andwater and softens the wood fibers. In steaming timber, live steam up to20 pounds gauge pressure is fed into the bottom of the treating cylinderby opening a. valve 9| in a pipe 92 connecting steam line 9 with thecylinder. After this steam has served its purpose the cylinder isrelieved of it by discharging it to atmosphere when valves 31, 48, and68 are opened. When the treating cylinder is free of live steam, a.vacuum of about 15 inches is created in the cylinder by means of theejector by opening valves l2, 13, 34, 35, 38, and 15. Then, withoutreducing this vacuum, the vacuum pump 11 is started to increase thevacuum to 24. inches or as may be required by opening valves 12, and 8|.When the vacuum pump is under way, the ejector is cut out. The sap andcondensate in the bottom of the cylinder are automatically drained of!durz the bottom of the cylinder.

a drum 94. V

In boiling timber, such as fir and oak, in preservative oil, the timberis first completely immersed in the preservative in the treatingcylinder leaving a small gas space between the top of the cylinder andthe preservative. The vacuum pump 11 is then started and thepreservatlveis boiled by the heat from the steam coils 42 in Thetemperature is maintained just a few degrees above the boiling point ofwater. As the moisture and sap are boiled from the timber the vacuumpump will pull the vapor into the condenser 19, and the condensate canbe drawn off and measured.

protecting the workers from harm, it also helps preserve valuablenatural resources.

According to the provisions of the patent statutes, I have explained theprinciple and mode of operation of my invention and have illustrated anddescribed what I now consider to be its best embodiment. However, Idesire to have it understood that, within the scope of the appendedclaims, the invention may be practiced otherwise than as specificallyillustrated and described.

I claim:

Wood-preserving apparatus comprising a treating cylinder for receivingwood to be impregnated with a liquid preservative in the cylinder, atank for the preservative connected to the cylinder,

a source of inert flue gas, a steam-actuated ejector for withdrawingsaid gas from said source and placing it under pressure, scrubbing andcooling means for the gas connected to the ejector, means connectingsaid scrubbing and cooling means with said tank, and selective means forconnecting the scrubbing and cooling means with said cylinder.

GRANT B. SHIPLEY.

